The overall goal of this project is to gain information that will improve current techniques for fitting hearing aids to infants and young children. The development of universal hearing- screening programs has created an urgent need for a well-defined scientifically-based approach for the selection and fitting of hearing aids with this population. Current hearing-aid technology is complex, requiring a large number of decisions during the fitting process. Studies with adults have shown large individual differences in hearing-aid benefit across listeners and subjective test techniques used to optimize the fit are not applicable with children. Furthermore, it has been argued that young hearing-impaired children may require different amplification characteristics than adults with similar hearing losses because children do not have the language structure or world knowledge to supplement communication. To date, no studies addressing the specific amplification needs of pre-lingually hearing-impaired children with mild to moderately-severe hearing loss have been conducted. The first aim of this project is to test the hypothesis that the acoustic needs of young hearing-impaired children change developmentally and differ from adults with hearing loss. The results of these studies should provide guidelines for age-appropriate hearing-aid fitting algorithms as well as basic information on the development of speech perception abilities in this population. The second aim is to test the hypothesis that hearing-impaired children can utilize multiple acoustic cues provided that the relevant aspects of the speech signal are sufficiently audible. These studies should enhance our understanding of auditory learning and acclimatization in relation to the hearing-aid fitting process. The final aim is to explore the role of auditory experience in early phonological, lexical, and morphological development. The goal is to identify early markers that would signal the need to modify amplification, alter intervention strategies, and/or explore the existence of additional disorders.